Hi Dilpree.
First of all, thanks for inviting me to bid.
Well, I'd like to know more about your business needs rather than the technical ones.
What are the main features you have in your current org?
How many customized objects your org has?
Are there many Apex pages and integrations with external sources?
What is the expected amount of data to be migrated (records)?
I believe that I can give you a better estimate once you provide these answers.
Regards.
Denis